Connector for an element of the coaxial type

ABSTRACT

The invention relates to a contact connection between a heating element of the coaxial type and a thicker connection pin. The connector comprises a sleeve closed by a pressure member in which a disk of soft sintered ceramic material is pulverized by moving said pressure member and is compressed as a compact mass around the bare part of the conductor projecting beyond the sheath, the end of the conductor being connected to the connection pin in a clamping connection.

United States Patent 1191 van Toorn Mar. 19, 1974 [54] CONNECTOR FOR AN ELEMENT F Tl-m 1,256,043 2/1918 Sabina et al. 337/236 COAXIAL TYPE 1,627,564 5/1927 \Loper 1. 219 541 2,427,291 9/1947 Marette et al. 338/229 X [76] Inventor: Cornelis Hendrik n n, 220,936 10/1879 McTighe 174/88 s Bennebroekerdijk 213, 2,489,013 11/1949 Dasher 174/88 S Haarlemmermeer, Netherlands [22] Filed: June 1971 Primary ExaminerDarrell I... Clay [21] Appl. No.: 155,599

[30] Foreign Application Priority Data 57 ST ACT June 23, 1970 Netherlands 7009163 June 23, 1970 Netherlands 7009164 The invention relates to a contact connection between a heating element of the coaxial type and a thicker /8 339/263 connection pin. The connector comprises a sleeve [51] Int. Cl H02g /08 closed by a pressure member in which a disk of soft F ield of Search 174/75 75 75 sintered ceramic material is pulverized by moving said 1 88 88 34 S, L 21 pressure member and is compressed as a compact 49 89 89 117 177 mass around the bare part of the conductor projecting 2 338/2 9/541; 337/236 beyond the sheath, the end of the conductor being connected to the connection pin in a clamping con- [5 6] References Cited nection.

UNITED STATES PATENTS 1,177,392 3/1916 6 Claims, 6 Drawing Figures Dempster 338/274 X CONNECTOR FOR AN ELEMENT OF THE COAXIAL TYPE The invention relates to a connector between a wireshaped element which comprises at least one electical conductor arranged in a metal sheath and insulated electrically by a metal oxide in powder form and an associated connection pin which is thick as compared with the conductor, in which connector the conductor, from which the insulation and sheath have been removed at its end, and a part of the pin are surrounded by a sleeve connected to the sheath, inside which sleeve a disk of an electrically insulating material is arranged between the pin and the sheath, and the free end of the bare conductor is connected to the pin. Such a connector is known from Dutch patent application 6,502,225 laid open to public inspection and in which the wireshaped element is a heating element.

In the known connector, the freely projecting, bare end of the conductor is threaded in an axial aperture of the connection pin and secured therein by means of a soldering operation. Furthermore, the sleeve which consists of a ceramic material is soldered both to the sheath of the element and to the connection pin. In this type of connector, the bare part of the conductor extending between the connection pin and the sheath of the element constitutes a zone which is critical both electrically and thermally and which is strongly decisive of the quality of the connection.

In addition, the application of this known type of connector is substantially restricted to those cases in which the entire construction can easily be subjected and exposed to a soldering operation.

It is the object of the invention to provide a rigid connector in which on the one hand a rapid heat dissipation over the said free part of the conductor can take place, the operating temperature of the connection pin remains low and furthermore any soldering operation may in principle be omitted.

For that purpose, the connector according to the invention is characterized in that, calculated from the end of the sheath inside the sleeve, the space between the pin and the sheath is filled with an electrically insulating material which closely surrounds the conductor and which preferably consists of a mass of a soft sintered ceramic material compressed around said part of the conductor, the free end of the conductor over a further part of its longitudinal dimension is connected to the thickened part of the pin facing the end of the sheath by means ofa clamping connection, and furthermore a pressure member which maintains the clamping connection is secured in the sleeve so as to be axially movable. So in this case a solution is used in which by means of the pressure member in the sleeve on the one hand the mass in the said critical zone is compressed around the end of the conductor projecting beyond the sheath and on the other hand the clamping connection between the end of the conductor and the pin is produced. Based on this idea, the invention provides a few embodiments for the way in which the clamping connection can be produced.

The connector in one of these embodiments is characterized in that the emanating conductor over the said further part of its length is surrounded by a disk of an electrically conducting material engaging the mass and is clamped over its end portion bent at right angles to the axis of the disk between the said disk and a pressure surface occurring on the thickened end portion of the pin. The end portion of the conductor which is bent at right angles is preferably coiled, which permits an extremely good energy transfer between the conductor and the pin.

In another embodiment, the relevant end of the conductor is clamped in a slot-shaped aperture of the thickened end of the pin, said aperture being reduced in size by cooperation between the pressure member and tapered wall parts of the thickened end of the pin. The rigid clamping connection is produced in this case by causing the axially movable pressure member to cooperate with one or more conical wall parts of the thickened end.

The pressure member can be moved over the pin by means of a member to be screwed in the sleeve, it being ensured that said movement preferably performs only a translation in the axial direction of the pin.

By using a screw movement to obtain a correct clamping effect, the possibility is obtained to arrange in the space inside the sleeve one or more rings of a soft sintered ceramic material around the parts to be connected prior to performing the clamping operation. When the pressure member is forced into the sleeve, said rings are pulverized and, while building up a large pressure in the sleeve, compressed to form a compact mass which centres the thickened part of the pin while efficiently enclosing the free end of the conductor and at the same time considerably compressing the insulating mass around the part of the conductor projecting beyond the sheath; such a connection therefore is very gas-tight.

In order that the invention may be readily carried into effect, it will now be described in greater detail, by way of example, with reference to the accompanying diagrammatic drawings, in which:

FIG. 1 is a longitudinal cross-sectional view of a first embodiment of the connector;

FIG. 2 is a part of a cross-sectional view taken on the line 11-11 of FIG. 1;

FIG. 3 is a longitudinal cross-sectional view of a second embodiment of the connector;

FIG. 4 is a cross-sectional view taken on the line IVIV of FIG. 3;

FIG. 5 is a longitudinal cross-sectional view of a third embodiment of the connector;

FIG'. 6 is a cross-sectional view taken on the line VI-VI of FIG. 5.

FIRST EMBODIMENT (FIGS. 1 AND 2) Reference numeral 1 in FIG. 1 denotes a resistance heating wire of the coaxial type. This wire comprises a metal sheath 2 and a central electrical conductor 3 which is insulated relative to the metal sheath 2 by a mass 4 of a metal oxide in powder form. At its one end the sheath 2 and the electrically insulating mass 4 have been removed from the wire 1. This part is denoted by 6 in the figure. In the heating wire shown, the sheath 2 has an outer diameter of 2.5 mm and the conductor 3 has a diameter from 0.1 to 0.15 mm. It is destined to supply watts per running centimetre. A sleeve 7 which is slightly conical is forced between a metal sleeve 8 and the sheath 2. Said sleeve 8 is secured in the housing, which is denoted diagrammatically by 9, by means of a screw connection. The part 6 of the conductor projecting from the sheath 2 is surrounded by a copper disk 10 comprising a central aperture through which the end 6 is threaded. The part of the wire extending through said disk 10 has a coiled end 11 (see also FIG. 2). The copper disk 10 is kept spaced from the bottom of the sleeve 8 by an electrically insulating member 12. This member is in the form of a disk and has been obtained by pulverizing a ring of a soft sintered ceramic material by means of a pestle and compressing it around the end 6.

The connector furthermore comprises a connection pin 13 which has a diameter of 2.2 mm and hence is approximately 15 times as thick as the central conductor 3. At its end, said pin 13 comprises a thickened portion 14 which is in the form of a disk. Said disk 14 bears with its flat part on the coiled part 11 of the conductor 6. The sleeve 8 furthermore comprises a compact mass 15, 16 likewise of a soft sintered ceramic material. Bearing on said mass 15, 16 is a pressure member 17 of a hard sintered ceramic material which has a diameter such that it can just be moved within the sleeve 8. Said pressure member 17 comprises a central aperture 18 through which the pin 13 can be inserted. The assembly is pressed down by a nut 19, if desirable with the interposition of a copper ring 20. In order to obtain a rigid connection, the mass 15, I6 originally is in the form of a few annular members l5, l6. By arranging said rings in the manner shown and moving the pressure member 17 down via the nut 19, said rings are pulverized.

By exerting a large pressure by means of the pressure member 17, any freely accessible space inside the sleeve 8 is filled with a compact mass of an electrically insulating material which, as it were, forms a continuation of the insulating mass 4 inside the sheath 2.

The heat dissipation in this connector has proved particularly favourable. Upon using the connector described in this embodiment for current strengths between 15 and 20 amp, the temperature of the connection pin remained constant at 50 C for a very long test period.

SECOND EMBODIMENT (FIGS. 3 AND 4).

The connector shown in FIGS. 3 and 4 comprises a wire-shaped heating element of the coaxial type the construction of which and the way of connecting the connection pin are essentially the same as those described with reference to FIG. 1. It is also destined to supply 150 watts per running centimetre. The part of the conductor 22 projecting beyond the sheath 21 is surrounded by a disk 23 of a soft sintered ceramic material comprising a central aperture through which the end 26 is threaded.

The connector furthermore comprises a hollow connection pin 33, the end of which the end is conical. Said end comprises a central aperture and a slot is provided by means ofa saw cut. The free end of the central conductor 22 is inserted in said slot. Reference numeral 36 denotes a pressure member of a hard sintered material which comprises cylindrical parts 37 and 38 and a conical aperture 39. Said pressure member 36 comprises a few longitudinal ribs which fit in associated longitudinal grooves 40 and 41 of the sleeve 28, so that said member can consequently be translated axially only in the sleeve 28. A nut 42 is slid over the pressure member and is screwed over a part of the sleeve 28 and encloses a sealing ring 45.

This connector is assembled as follows.

The sleeve 28 is screwed in the housing 49. The copper sleeve 47 with the element 51 is then forced into the sleeve 28; no soldering operation is used. The ceramic disk 23 is then placed over the freely projecting end and, if desirable, is pulverized by a pestle of a suitable shape so that the resulting insulating mass is compressed around the projecting conductor. The pin 33 is then placed over the end of the conductor. The pressure member is then provided and the assembly is closed by a nut 42. By tightening the nut 42, the pressure member 36 is moved axially, the two parts 53 and 54 of the pin 33 separated by the slot being forced towards each other. During this axial movement the mass obtained from the disk 23 is further compacted. while at the same time the free end of the conductor is clamped between the parts 53 and 54. If desirable, an

extra ring 52 likewise of a soft sintered ceramic material may be clamped between the pressure member 36 and the disk 23 and be pulverized by said pressure member. The resulting connector is highly gas-tight. It will be obvious that the contact connection can also be produced without previously pulverizing the disk 23; in that case, all disks and rings present and consisting of a soft sintered material are pulverized in one operation by means of the pressure member 36. Ambient air cannot penetrate to the end of the conductor projecting beyond the sheath. A good heat dissipation from said conductor end to the pressure member 36, sleeve 28 and housing 49 is also ensured. It has been found that when the connector is used for a prolonged period of time with a current strength of l0 amp, the pin 33 which has an outer diameter of 3 mm assumes an operating temperature of at most C.

THIRD EMBODIMENT (FIGS. 5 AND 6).

In the embodiment shown in FIGS. 5 and 6, a wireshaped heating element 55 is used which comprises two conductors 57 and 58 surrounded by a metal sheath 56. In this embodiment also, an electrically insulating mass 59 of metal oxide in powder form is present both between the conductors mutually and between the conductors and the sheath. In general, the construction of the connector is analogous to that of the embodiments described with reference to FIGS. 1, 2, 3 and 4. In this embodiment, however, two free ends 60 and 61 project beyond the sheath, the disk 66 of a soft sintered ceramic material comprises two apertures for passing through the conductors, and the cylindrical connection pin 72 is composed of three parts 73, 74 and 75. In this case the part 74 is a strip of a hard sintered ceramic material and the parts 73 and 75 are of copper, the crosssections of which are segments of a circle. Said parts 73 and 75 comprise at their ends tapered thickened parts 76 and 77, respectively, in which apertures 78, 79 and saw cuts 80, 81 are provided in a manner corresponding to that of the connector shown in FIGS. 3 and 4. The free ends 60 and 61 of the conductors 57 and 58 project to said saw cuts; if desirable, said ends may project through the apertures 78 and 79 to beyond the pin 72. In this connector also, a pressure member 82 of a hard sintered ceramic material is used which can be moved in the sleeve 83 in the axial direction only. In this case also, a ring 86 likewise of a soft sintered ceramic material may be arranged between the pressure member 82 and the disk 66, in a manner analogous to that of FIG. 3. A nut 84 again terminates the construction. The connector is manufactured in a manner analogous to that of the construction described with reference to FIGS. 1 and 3. By tightening the nut 84, the pressure member 82 is moved downwards and the parts 76 and 77 are forced towards each other by the walls of the tapering aperture in the pressure member, the strip 74 serving as an anvil. Consequently, the free ends 60 and 61 of the conductors are secured to the copper parts 73 and 75 in an efficient manner. In this manner of connecting also, an extremely efficient heat dissipation to the other places than the copper parts 73 and 75 is ensured. In a practical embodiment, in which the conductor 58 served as a filament and the conductor 57 served as a temperature detection wire, an operating temperature of 50 C of the parts 73, 74, 75 was measured with a current strength of amp. for a prolonged period of time.

As stated above a few times, a soft sintered ceramic material is used. For said material may be used advantageously, the material known commercially as GIR- ALUMlNE."

The constructions described are particularly suitable for use as a connection of connection terminals at the ends of a heating element of the coaxial type. It has been found that they can even stand considerably vary ing loads.

The invention has been described with reference to an embodiment for a heating element of the coaxial type. Of course, the invention is not restricted to this field of application. It may also be used for the connection ofa coaxial cable for measuring purposes, in which the sheath is electrically connected to the mass of the housing.

A further advantage of the connector according to the invention which requires only few components is that it is readily detachable, for example, for purposes of repair and/or inspection.

Still a further advantage is that soldered joints are not necessary. This provides the possibility of producing the connection without the use of particular heat sources. Since, moreover, only few components are used in the connection according to the invention, it is particularly suitable for use in assembly places which are difficult of access.

I claim:

1. An electrical connection between a connecting pin and that part of an electrical conductor which extends within and beyond a metal sheath, the connecting pin having a larger cross-section than said conductor, comprising a sleeve supporting said sheath with its electrical conductor electrically insulated therefrom, said sleeve having a portion surrounding in spaced relation both the extending part of the electrical conductor and an end of the connecting pin, annular clamping means integrally formed with said connecting pin at said end thereof surrounded by said sleeve and being disposed in clamping engagement with said extending part of the conductor, electrically insulating material being disposed within said sleeve and filling the space around said extending part of said conductor and closely surrounding said extending part of the conductor, an axially movable pressure member received at least in part within said sleeve portion and overlying said annular clamping means and applying pressure thereon, and means mounted in relation to said pressure member for moving the latter axially relative to said sleeve and exerting pressure on said annular clamping means and electrically connecting the latter solely with said extending part of the conductor, said annular clamping means comprising an enlarged end section facilitating the connection of the larger cross-sectional connecting pin and the smaller crosssectional conductor.

2. An electrical connection according to claim 1, in which said annular clamping means comprises a cylindrical enlargement on the connecting pin, said extending part of said conductor having an end portion bent in substantially perpendicular relation to said extending part and providing a surface engaged and clamped by said cylindrical enlargement.

3. An electrical connection according to claim 2, in which said end portion of the extending part of said conductor is bent into coil form.

4. An electrical connection according to claim 1, in which said annular clamping means comprises (a) a conical enlargement having an outer surface cooperating with a conical surface formed on said pressure member, the base of the conical enlargement having an axially extending slot-shaped aperture in which said extending part of the conductor is received and is clamped.

5. An electrical connection according to claim- 1, in which said means for moving said pressure member comprises a nut threadedly engaging said sleeve and bearing against said pressure member.

6. An electrical connection according to claim 1, in which one of said pressure member and said sleeve is provided with an axially extending rib fitting in an axially extending groove formed in the other of said pressure member and said sleeve. 

1. An electrical connection between a connecting pin and that part of an electrical conductor which extends within and beyond a metal sheath, the connecting pin having a larger cross-section than said conductor, comprising a sleeve supporting said sheath with its electrical conductor electrically insulated therefrom, said sleeve having a portion surrounding in spaced relation both the extending part of the electrical conductor and an end of the connecting pin, annular clamping means integrally formed with said connecting pin at said end thereof surrounded by said sleeve and being disposed in clamping engagement with said extending part of the conductor, electrically insulating material being disposed within said sleeve and filling the space around said extending part of said conductor and closely surrounding said extending part of the conductor, an axially movable pressure member received at least in part within said sleeve portion and overlying said annular clamping means and applying pressure thereon, and means mounted in relation to said pressure member for moving the latter axially relative to said sleeve and exerting pressure on said annular clamping means and electrically connecting the latter solely with said extending part of the conductor, said annular clamping means comprising an enlarged end section facilitating the connection of the larger cross-sectional connecting pin and the smaller cross-sectional conductor.
 2. An electrical connection according to claim 1, in which said annular clamping means comprises a cylindrical enlargement on the connecting pin, said extending part of said conductor having an end portion bent in substantially perpendicular relation to said extending part and providing a surface engaged and clamped by said cylindrical enlargement.
 3. An electrical connection according to claim 2, in which said end portion of the extending part of said conductor is bent into coil form.
 4. An electrical connection according to claim 1, in which said annular clamping means comprises (a) a conical enlargement having an outer surface cooperating with a conical surface formed on said pressure member, the base of the conical enlargement having an axially extending slot-shaped aperture in which said extending part of the conductor is received and is clamped.
 5. An electrical connection according to claim 1, in which said means for moving said pressure member comprises a nut threadedly engaging said sleeve and bearing against said pressure member.
 6. An electrical connection according to claim 1, in which one of said pressure member and said sleeve is provided with an axially extending rib fitting in an axially extending groove formed in the other of said pressure member and said sleeve. 